Synthesis of the <i>C</i>-Linked Disaccharide α-<scp>d</scp>-Man-(1→4)-<scp>d</scp>-Man Employing a SmI<sub>2</sub>-Mediated <i>C</i>-Glycosylation Step: En Route to Cyclic <i>C</i>-Oligosaccharides
作者:Lise Munch Mikkelsen、Troels Skrydstrup
DOI:10.1021/jo020585a
日期:2003.3.1
Investigations are reported on the assembly of the C-linked disaccharide alpha-D-Man-(1-->4)-D-Man, representing the first steps in our projected synthesis of a cyclic C-oligomer containing repeating units of this C-dimer. The key step in this synthesis uses a SmI2-mediated coupling of 2,3,4,6-tetra-O-benzyl-alpha-D-mannopyranosyl 2'-pyridyl sulfone with a C4-formyl branched mannopyranoside unit, affording the C-disaccharide derivative with complete stereocontrol at the two new stereogenic centers. Subsequently, a modified tin hydride based deoxygenation produced the target carbohydrate analogue. The synthesis of the C4-formyl monosaccharide makes use of a stereoselective radical-based allylation followed by double bond migration and ozonolysis.